As the oil and gas industry continues to search for and access new sources of fossil fuels, it produces an enormous amount of waste product requiring treatment. For example, in the process for drilling for oil, drill cuttings tainted with hydrocarbons are forced to the surface.
Currently most drill cutting waste is landfilled. This disposal method relies on the disposal of hydrocarbons in the waste material using the soils natural microbes to breakdown the oils over a period of time. The process does carry some risk as there is a possibility that some of the oils and other organic compounds can leach into the water system causing environmental and economic damage. In addition, higher molecular weight compounds breakdown at a much slower rate than some of the materials and tend to contaminate the sites over longer periods of time.
Accordingly, a number of technologies have been developed for dealing with drill cuttings or other carbonaceous feedstock such as waste from the oil sands. These include the following:                Grinding: There are some technologies that use grinding or other similar methods to convert mechanical energy to heat in order to drive off the volatiles so the remaining waste material can be landfilled. These are generally quite expensive and tend to use a lot of energy. An example of such a grinding system is taught in International Publication No. WO 2006/003400 (Garrick). Garrick teaches a reactor vessel for treating contaminated waste products, such as drill cuttings. Waste material input into the reactor is heated so as to change the phase of the contaminant so it can be removed and the treated material discharged. Heat is generated in the reactor vessel by friction between spinning flails and a grinding material (dry powder) introduced into the reactor. Alternatively, additional external heating can be provided by a heating jacket.        Land farming: By adding a number of chemicals to the landfill process, the environmental impact of some of the compounds that tend to build up in the soils and water table can be reduced. A method of turning the material is used to expose more surface area to air to accelerate the evaporation process. However releasing hydrocarbons to the air can create additional environmental issues. Furthermore, over time, some of the compounds will build up on the soils and water table with consequent environmental impact.        Thermal Desorption Systems (TDU)—High Temp/Low Temp: Most TDU plants tend to be large and centralized. In the case of high temp TDU systems, high volumes of air and an outside energy source are employed to reach temperatures adequate to vaporize the hydrocarbons. The energy from this process is sometimes used for other applications such as drying, etc. High temp TDU systems often reach temperatures well above coking/molecular change levels and are not typically able to recover hydrocarbons in a useful form. Low temperature TDU systems employ a much more controlled process using low temperature levels, around 500 F, and are able to effectively remove up to 70% of the hydrocarbons present in the cuttings. These systems are also able to recover the liquid hydrocarbons in a form that can be beneficially reused. Outside energy sources are required at a cost and therefore the plants tend to be large centralized facilities due to energy economics and the size and configuration of equipment available.        Gasification: Gasification is the production of a combustible gas from a carbonaceous feedstock. International Publication No. WO2011/142829 (Swetnam) teaches a gasifier system for decomposing organic matter such as waster rubber tires, coal, oil shale, tar sands, etc. Swetnam teaches a reaction vessel within a thermally insulated enclosure, the bottom surface of the reaction vessel being heated by burners so as to decompose waste materials within the reaction vessel. A rotating paddle is used to agitate the waste material within the reaction vessel. Exhaust gases from the waste material exit through an exit port where they can be recovered and reused. Burners are inefficient, running at approximately 3500 to 4000 F and creating hot spots and localized elevated temperatures in the processed material causing coking and cracking.        
Accordingly, there is a need for a more efficient gasifier for treating waste material.
Objects of the invention will be apparent from the description that follows.